tcp remote ports question

Posted on 2004-11-16
Last Modified: 2013-11-29

Most people know that you could go to a website like to find out your ip and other browser environmental variables.  On, you can see your "remote port" also... I was under the impression that TCP/IP ports are always from 0-9999, yet the remote port listed is a 5-digit port.  Not only that, but it changes every couple of seconds when I refresh.

I am connected to the internet via a cable modem with comcast as my ISP.  I am getting the address via DHCP...  The remote port is also showing up on access logs of devices that my computer logs onto in remote devices... what is this thing for and how is it different from TCP/IP ports?

Question by:meuedyn
    LVL 41

    Accepted Solution

    there are over 64000 tcp ports
    the way it works is (using http as an example) your machine sends a packet out with the destination port of 80, but it requests the packet be sent back at a dynamically designated port, so that is why it changes when  you refresh
    LVL 41

    Expert Comment

    actually there are  65535 possible ports officially recognised
    LVL 8

    Assisted Solution

    The port number range on a system is from 0-65535, of these the port range from 0-1024 is called as the reserved or well known ports. the range from 1025-49300 is called as the registered port and all ports above that are called as dynamic ports.
    check this link for a detailed listing of all the pors

    As stevenlewis pointed out, the system would send the request to the port 80 of the server, but the reply would come to one of the registered ports specified by the browser.
    This is what helps us to use the same internet connection but have multiple simultaneous web sessions on the same system ( one google window, another running yahoo etc) each browser instance would be using a different port so that when i click on one link in yahoo, the result is not displayed in the google window but comes only in the yahoo window.

    Author Comment

    So I request a webpage from port 80 (of the server) and send a "remote port" along with the packet so that server knows to send the information requested to my ip address at the "remote port"?

    Does it change for every web page I request?
    LVL 41

    Expert Comment

    Yes, and Yes
    LVL 10

    Expert Comment

    Hi meuedyn,
    Right, the HTTP server listens on port 80. However, your browser, and other client applications, send requests and receive responses on arbitrary high-numbered ports.


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